Robotic systems are commonplace in fields such as manufacturing. Indeed, manufacturing plants typically employ robotic systems including numerous robotic manipulators to perform various tasks. To avoid damage to the robotic manipulators, it is helpful to control the robotic manipulators according to a collision avoidance scheme. As such, a variety of collision avoidance schemes for robotic systems have been developed.
Some collision avoidance schemes work by constraining each robotic manipulator to pre-planned collision free paths. For example, one such collision avoidance scheme is disclosed in U.S. Pat. No. 5,204,942 to Otera et al. Such a collision avoidance scheme typically requires reprogramming to accommodate each and every change made to the pre-planned paths of the robotic manipulators. In a manufacturing process that is routinely altered and updated, the collision avoidance system of Otera et al. may be disadvantageous due to the necessary repeated reprogramming thereof.
Other collision avoidance schemes may model a workspace and divide it into different zones. Certain robotic manipulators may be forbidden to enter certain zones, or only one robotic manipulator may be allowed into a given zone at a time. U.S. Pat. No. 5,150,452 to Pollack et al. discloses such a collision avoidance scheme for a robotic system. The robotic system includes a controller storing a model of the workspace that is divided into an occupancy grid. The controller controls the robotic manipulators of the robotic system such that only one robotic manipulator may occupy a cell of the occupancy grid at a given time. This collision avoidance system may reduce the efficiency of a manufacturing plant, particularly if there are a variety of differently sized robotic manipulators and the cell sizes of the occupancy grid are sized to accompany the largest robotic manipulators. Further, since this robotic system operates based upon a model of the workspace, any change to the workplace may require an update of the model, which may be time consuming.
Other attempts at collision avoidance schemes for robotic systems include a controller that actively looks for potential collisions between robotic manipulators. For example, U.S. Pat. No. 4,578,757 to Stark discloses a collision avoidance scheme for a robotic system that models each robotic manipulator of the system as a number of overlapping spheres. As the robotic manipulators move along pre-planned paths, the distance between each sphere of nearby robotic manipulators is calculated by a controller. These calculated distances indicate a risk of collision between two adjacent robotic manipulators. When the risk of collision exceeds a threshold amount, at least one of the robotic manipulators may be slowed down as it travels along its pre-planned path, or even stopped completely. Such a collision avoidance scheme, however, may reduce the efficiency of a manufacturing plant employing the robotic system due to the stopping of robotic manipulators and the associated delays in the manufacturing process.
As explained, these prior approaches may render a manufacturing process employing their respective robotic systems inefficient. Moreover, robotic systems employing these prior approaches may be difficult and/or costly to adapt to new applications or to the addition of additional robotic manipulators. As such, further advances in the field of collision avoidance schemes may be desirable.